YM fog ?

The definitions of transponder and transceiver aren't really consistent across various branches of electronics.

If the IMO want to call it 'transponder', they probably can. It's their system.
 
lw395 said:
The definitions of transponder and transceiver aren't really consistent across various branches of electronics.

If the IMO want to call it 'transponder', they probably can. It's their system.
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I don't believe that it is illegal either.
 
Minn said:
Exactly.

Older container ships, designed for double that speed but probably making thirteen, have hatchet shaped bows and won't throw a yacht aside.
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Not a great deal of those in use anymore. Most box ships have a bulbous bow, so there's still some chance you'll get pushed away by the bow wave it is designed to generate. Not that I want to get close enough to ever test that theory.
 
lw395 said:
An AIS set is a transponder.
The A stands for automatic.
Your AIS transmits in response to the network (of which it becomes a part). You cannot autonomously transmit with your AIS. It's not really a transceiver in any useful or conventional sense.
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That's interesting, thanks for the info, because I had likewise assumed that a yacht AIS transmitted blind to any stations capable of hearing it, rather than in response to being interrogated. You learn something every day..
 
Ladybirdgaffcutter said:
That's interesting, thanks for the info, because I had likewise assumed that a yacht AIS transmitted blind to any stations capable of hearing it, rather than in response to being interrogated. You learn something every day..
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Having read subsequent posts, and thinking about it, I am actually coming to the view that the AIS must be transmitting blind.
Anyway, not getting into an argument.. but it's all very educational..
 
Ladybirdgaffcutter said:
Having read subsequent posts, and thinking about it, I am actually coming to the view that the AIS must be transmitting blind.
Anyway, not getting into an argument.. but it's all very educational..
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Heres all you need to know about the implementation of Self Organised Time Division Multiple Access (SOTDMA) for AIS...
http://www.allaboutais.com/index.ph...-technicals/technical-lfundamentals/93-sotdma

Even mid-ocean its not quite blind as it will still transmit into a defined time slot, hence Self Organised
 
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RobbieW said:
Heres all you need to know about the implementation of Self Organised Time Division Multiple Access (SOTDMA) for AIS...
http://www.allaboutais.com/index.ph...-technicals/technical-lfundamentals/93-sotdma

Even mid-ocean its not quite blind as it will still transmit into a defined time slot, hence Self Organised
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The 'self organised' label really means that among a cluster of ships, the AIS organises itself, there is no 'master' telling each ship what its time slot is, they are all equally applying the same algorithm to pick their slot. Most TDMA systems have some sort of hierarchy, such as a base station allocating slots to mobiles.
 
lw395 said:
The definitions of transponder and transceiver aren't really consistent across various branches of electronics. If the IMO want to call it 'transponder', they probably can. It's their system.
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It is not a pure transponder, as they only transmit in response to incoming signal and this beast tries to transmit on its own- in my engineering transport world we use transponders as self powered semi-passive beacons to mark speed and operational changes- but to call it a transceiver is wrong as disregards important functionality
 
RichardS said:
It's a receiver and a transmitter so a transceiver, albeit an automatic one, although I don't see why that would make any difference. :confused:

Richard
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It's actually 2 or 3 receivers and a transmitter...
Or at least the ones I worked on were.
Things may have changed a bit as that was a couple of boats ago.
 
dom said:
I'm not an RYA instructor, but I'd personally recommend exactly the opposite and strongly so. In fact, I would feel much safer with an operational radar set and decently specced radar reflector like an Echomax 230.

Trouble with AIS-only is that one could for example be altering course in good time to avoid an AIS transmitting ship, thereby setting up a conflict with a non-transmitting fishing boat or yacht which had hitherto given way and expected you to hold your course under Rule 17a (i).

Aside from the many Colreg problems of being blind to non-transmitting vessels, radar can provide invaluable info during the pilotage port-entry stage. Finally there is the matter that other vessels will expect an AIS transmitting vessel to be radar equipped, increasing their element of surprise if the boat does something ostensibly daft. And surprise here = danger.

So for me, I'd recommend radar all the way.
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Well I’d never recommend exactly the opposite. Ie radar and no AIS. You can get an AIS receiver for under £100 and it is better at SHIP avoidance than radar in many respects

Not only does it clearly show CPA (this is not that easy on radar MARPA isn’t great on small boats and you have to actively intervene) but it shows heading, ROT and SOG. It also gives the vessel name.

I’ll give you a real example. Being overtaken by a tanker., CPA 80ft TCPA about 10 minutes. I called the tanker by name and told the master of my intention to stand on. He thanked me and turned to starboard by 2 degrees. I could see he had turned immediately even though the CPA dances around a bit it takes a while to trust the change. . All a radar would have done is give me brown trousers.

Also when monitoring CPA by MARPA or AIS it is (obviously) only a good estimate if both vessels maintain course and speed. Often masters nudge up by a degree or two to avoid a smal vessel traversing the channel. You can see that move before you trust the change in CPA. This avoids him altering course, you altering course because he’s big and so on. You have an obligation to stand on remember. AIS can help make that judgement BETTER than radar.

Of course radar can do loads AIS can’t. Squalls don’t transmit an AIS signal for example, nor as you quite rightly pointed out, do all vessels or rocks. But radars are expensive.

So why would I never recommend the opposite as you suggest.? If you can afford radar then have both, in boat terms the AIS cost is trivial.. Overlaid they make for a powerful contribution to decision making.
 
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lw395 said:
An AIS set is a transponder.
The A stands for automatic.
Your AIS transmits in response to the network (of which it becomes a part). You cannot autonomously transmit with your AIS. It's not really a transceiver in any useful or conventional sense.
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Beg to differ, greatly.
It is not a transponder.
It does not transmit in response to anything. It transmits, period.
It also receives.
The two activities occur independantly.
It is a transceiver.
 
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